Method of making a dental product

ABSTRACT

The invention provides high strength dental polymeric dental products made from wax-like polymerizable dental material. These dental products have superior strength compared to products formed from prior wax-like polymerizable materials. Prior wax-like polymerizable materials do not form strong enough polymeric material for making dentures. High strength dentures are made by positioning artificial teeth in wax-like polymerizable dental material of the invention. This material is then shaped and polymerized to the form a denture base of high strength dental polymeric material. These dentures are completed without forming wax and without applying inorganic plaster to the artificial teeth.

This application is a continuation of application Ser. No. 09/682,440,filed Sep. 4, 2001 now U.S. Pat. No. 6,592,369.

DETAILED DESCRIPTION

The invention relates to wax-like polymerizable materials. The inventionprovides wax-like polymerizable dental materials, and methods of formingdental products of high strength dental polymeric material. Thiswax-like polymerizable dental material is quickly and easily reshaped.It is reshaped by warming, and shaping while warm and then allowing itto cool to room temperature. The shaped wax-like polymerizable dentalmaterial is cured to form dental products. These dental products havesuperior strength compared to products formed from prior wax-likepolymerizable materials. Prior wax-like polymerizable materials do notform strong enough polymeric material for making dentures. High strengthdentures are made by positioning artificial teeth in wax-likepolymerizable dental material of the invention. The disclosures of U.S.patent application Ser. No. 09/670,364 filed Sep. 26, 2000 and U.S.provisional patent application Ser. No. 06/237,523 filed Oct. 4, 2000are incorporated herein by reference in their entirety.

Volkel et al in U.S. Pat. No. 6,057,383 (and Canadian Patent Application2207351), assigned to Ivoclar, disclose wax-like polymerizable materialfor making entire dental products. The prior art does not disclose awax-like polymerizable material for forming dentures or other highstrength products.

The invention provides a high strength dental polymeric material formedfrom wax-like polymerizable dental material. High strength dentalpolymeric dental products include partial dentures and full dentures.

Working wax-like polymerizable dental material, often includes molding,shaping, and/or carving. When heated, wax-like polymerizable dentalmaterial softens. In its softened state, it is believed to be partiallycrystalline and have a flowable amorphous phase, which allows someflowability of the material. Preferably, wax-like polymerizable dentalmaterial is dimensionally stable below 24° C. and softened at and above24° C. More preferably it is softened at and above 30° C. By heatingfrom its dimensionally stable condition, wax-like polymerizable dentalmaterial of the invention undergoes a rapid transition to being freelyflowable. By cooling from its softened state, wax-like polymerizabledental material of the invention undergoes a rapid transition to beingdimensionally stable. Small volumes of wax-like polymerizable dentalmaterial may be worked, while being warmed on the dental device. Theymay be dispensed from a heated syringe-type dispensing device, spatula,electric spatula, disposal dropper or other mechanical or electricaldispenser. To make a denture, wax-like polymerizable dental material ispositioned on a polymeric base plate made from an impression of apatient's mouth. Artificial teeth are positioned in the wax-likepolymerizable dental material, which is then shaped by melting andresolidifying. Then the wax-like polymerizable dental material ispolymerized to form a denture. Thus the denture is formed withoutapplying inorganic plaster to the artificial teeth and withoutpositioning artificial teeth in a mold as required by conventional lostwax or other similar prior art methods of forming a denture. Compounds,which are readily partially crystallizable and useful in wax-likepolymerizable dental material of a preferred embodiment of theinvention, include methacrylate (or acrylate) compounds prepared forexample by reaction of a urethane pre-oligomer withhydroxylalkymethacrylate. Preferably such compounds have a structurewithin the scope of one of general formulas I–V below. Preferably theurethane pre-oligomer is linear, comprises isocyanate end groups and hasa structure within the scope of general formula I:OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—R₁—NCO  I

wherein R₁ and R₂ are either an alkyl having from 1 to 14 carbon atomsor containing at least an aromatic group having from 6 to 14 carbonatoms, m is an integer from 0 to 20, the value of m in the oligomerdepends on the molar ratio of diisocyanate to diol used, and the valueof m increases as this molar ratio decreases. The diisocyanate portionhas the structure OCN—R₁—NCO and the diol portion has the structureHO—R₂—OH.

Alternatively, urethane pre-oligomer is formed by reaction of at leastone diol with excess, at least one diisocyanate to yield a urethanepre-oligomer having a structure within the scope of one or more ofgeneral formulas: II–IV

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General Formulas:II–IV OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)— II(R₁—NH—CO—O—R′₂—O—OC—NH)_(n)—R₁—NCOOCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—(R″₁— IIINH—CO—O—R₂—O—OC—NH)_(n)—R′₁—NCO OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—(R″₁— IVNH—CO—O—R′₂—O—OC—NH)_(n)—R′₁—NCO

wherein R₁, R′₁, R₂ and R′₂ each independently is an alkyl having from 1to 14 carbon atoms or at least an aromatic group having from 6 to 14carbon atoms, n and m are each independently integers from 0 to 20, thesum of n and m in the oligomer depends on the molar ratio ofdiisocyanates to diols used, and the value of the sum of n and mincreases as this molar ratio decreases. The diisocyanates have thestructures OCN—R₁—NCO and OCN—R′₁—NCO and the diols have the structuresHO—R₂—OH and HO—R′₂—OH. The more complex structures of urethanepre-oligomer are constructed from at least two different diols and atleast two different diisocyanates.

Reaction of the urethane pre-oligomer with the ethylenically unsaturatedmonomer as defined below yields a polymerizable compound having thestructure within the scope of the general formulaV:CH₂═C(R₃)—CO₂—R₄—CO—NH—(R₁—NH—CO—O—R₂—O—OC—NH)_(n)—R₁—NH—CO—R₄—O₂C—C(R₃)═CH₂Vwherein R₃ is hydrogen, or an alkyl, such as a methyl group, and R₄ isan alkyl group having from 1 to 14 carbon atoms, and n is an integerfrom 0 to 20. The typical ethylenically unsaturated monomer is ahydroxyalkyl (meth) acrylate, e.g. 2-hydroxyethyl methacrylate,hydroxypropyl methacrylate, caprolactone 2-(methacryloyloxy) ethylester, etc.

Preferred mechanical properties of cured resin and the adequate handlingproperties of compositions, polymerizable compound, are present when thevalue of n in the compound is not greater than 10; more preferably n isnot greater than 5. The preferred value of n in the compound largelydepends on the requirements of the specific application. The mostpreferable value of n in the compound for aromatic ring based diol isbetween 1 and 3. Therefore, the molar ratio of diisocyanate to diol foraromatic ring based diol is most preferable between 1.33 and 2. The mostpreferable value of n in the compound for alkyl based diol is between 1and 4. Therefore, the molar ratio of diisocyanate to diol for alkylbased diol is most preferable between 1.25 and 2.

Catalysts known in the art may be used to accelerate the formation ofthe isocyanate-ended pre-oligomer and end-capped ethylenicallyunsaturated monomer, for examples, tertiary amines and metal salts, e.g.stannous octoate and in particular dibutyl tin dilaurate. Preferredstabilizers used in this invention are butylated hydroxytoluene (BHT)and the methyl ether of hydroquinone (MEHQ).

Preferably compounds of the invention are difunctional methacrylatesincluding reaction products of bisphenol A propoxylate,1,6-diisocyanatohexane and 2-hydroxyethyl methacrylate, reactionproducts of bisphenol A propoxylate, trimethyl-1,6-diisocyanatohexaneand 2-hydroxyethyl methacrylate, a series of reaction products ofbisphenol A, trimethyl-1,6-diisocyanatohexane and 2-hydroxylethylmethacrylate, a series of reaction products of bisphenol A,1,6-diisocyanatohexane and 2-hydroxylethyl methacrylate, a series ofreaction products of trimethyl-1,6-diisocyanatohexane,2,5-dimethyl-2,5-hexanediol and 2-hydroxyethyl methacrylate, a series ofreaction products of trimethyl-1,6-diisocyanatohexane,1,6-diisocyanatohexane, 2,5-dimethyl-2,5-hexanediol and 2-hydroxyethylmethacrylate, a series of reaction products oftrimethyl-1,6-diisocyanatohexane, 1,6-diisocyanatohexane, bisphenol Apropoxylate and 2-hydroxyethyl methacrylate, caprolactone2-(methacryloyloxy)ethyl ester, and derivatives of above compounds.

Diisocyanates useful for making wax-like polymerizable dental materialof the invention include trimethyl-1,6-diisocyanatohexane,1,6-diisocyanatohexane, 1,8-diisocyanatooctane, isophorone diisocyanate,4.4″-methylenebis(cyclohexyl isocyanate), cyclohexyl diisocyanate,3-methylhexane-1,6-diisocyanate, 3-ethyl-1,6-hexanediisocyanate,5-methyl-1,9-nonanediisocyanate, 5-ethyl-1,10-decanediisocyanate,2,3-dimethyl-1,6-hexanediisocyanate,2,4-dimethyl-1,8-octanediisocyanate,2,4,6-trimethyl-1,7-heptanediisocyanate,2,3-dimethyl-5-ethyl-1,8-octanediisocyanate,2-methyl-4,6,8,10-tetrapropyl-1,12-dodecanediisocyanate and the like,and mixtures thereof. Examples of diisocyanates that are also suitableinclude aromatic diisocyanates, for example, 4,4-methylene bis(phenylisocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,1,4-phenyl diisocyanate, 1,5-naphthalene diisocyanate, 1,3-bis(isocyanatomethyl)benzene, 1,3-bis(isocyanato-1-methylethyl)benzene,1,3-bis(isocyanatomethyl)cyclohexane, 3,3″-bitoluene diisocyanate,1,4-xylylene diisocyanate and the like, and mixtures thereof.

Examples of diols useful for making compounds for wax-like polymerizabledental material of the invention include 1,4-butanediol, 1,6-hexanediol,1,10-decanediol, 1,9-decanediol, 1,12-dodecanediol,1,14-tetradecanediol, 2,5-dimethyl-2,5-hexanediol, hydrogenatedbisphenol A, bisphenol A, propoxylated bisphenol A, ethoxylatedbisphenol A, bis (2-hydroxyethyl)terepthalate, and mixtures thereof.

Examples of methacrylates (or acrylates) useful for making compounds forwax-like polymerizable dental material of the invention include2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylmethacrylate, 3-hydroxypropyl methacrylate, hydroxypropyl acrylate,glycerol dimethacrylate, glycerolmonomethacrylate, 2-hydroxyethylacrylate, hydroxypropyl acrylate, 4-hydroxybutyl methacrylate,4-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate,2-hydroxycyclohexyl methacrylate, caprolactone 2-(methacryloyloxy)ethylester, pentaerythritol triacrylate, 2-hydroxycyclohexyl acrylate andmixture thereof.

Wax-like polymerizable dental material may include one or moreinitiating systems to cause them to harden promptly. Light curablewax-like polymerizable dental materials preferably include a lightsensitizer, for example camphorquinone, Lucirin TPO, or methyl benzoinwhich causes polymerization to be initiated upon exposure to activatingwavelengths of light; and/or a reducing compound, for example tertiaryamine.

A room temperature or heat activating catalyst system is preferablyincluded in the wax-like polymerizable dental material of the invention.Preferably included is a peroxide capable of producing free radicalswhen activated by a reducing agent at room temperature or by heating.Preferred peroxides include benzyl peroxide and lauroyl peroxide.

Wax-like polymerizable dental materials of the invention are believed torapidly partially recrystallize. This rapid recrystallizability providesa unique combination of free flowability and dimensional stability,depending on its temperature. It is believed that the material rapidlytransitions from a freely flowable state by means of rapidcrystallization to a dimensionally stable state. The material atsolidification temperatures is partially crystalline and thecrystallinity present in an amorphous phase results in the effectivedimensional stability of the material. “Crystallinity” as used hereinrefers to regularity and order within a material resulting in a heat offusion of at least 1.0 J/g at and below 50° C. Heat of Fusion as usedherein refers to enthalpy of fusion as determined by ASTM 793-95.Percent crystallinity is determined by measuring the heat of fusionusing differential scanning calorimetry according to ASTM test method E793-95.

The wax-like polymerizable dental material of the invention is usefulfor formation of dental products including full dentures, partialdentures, denture liners, custom trays, artificial teeth, repairs fornatural teeth, veneers, denture repairs, denture reline, night guards,splints, retainers, orthodontic components, crowns, bridges, provisionaldental devices, inlays, onlays, and tooth restorative fillings,orthodontic appliances, oral orthopedic appliances, temporary dentures,temporary partial dentures; maxillofacial prostheses, obturators, andoccular prostheses.

Compositions in accordance with the invention may further includefillers, pigments, stabilizers, plasticizers and fibers. Preferably,polymerizable dental compositions in accordance with the inventioninclude from about 2 to about 95 percent by weight filler particles.More preferably, these compositions include from about 10 to about 85percent by weight filler. Nanocomposites and ceramers may be formed fromthese composites. The fillers preferably include both organic andinorganic particulate fillers to further reduce polymerizationshrinkage, improve wear resistance and modify the mechanical andphysical properties.

A preferred embodiment of the invention provides a high strength dentalpolymeric material formed by light curing wax-like polymerizable dentalmaterial shaped into at least a portion of a denture base. Preferablythe wax-like polymerizable dental material has a flexural modulus of atleast 400,000 psi and a flexural strength of at least 7,000 psi and anun-notched impact strength of at least 2 foot-pounds/inch. Preferablythe denture comprises denture base, and a tooth comprising aninterpenetrating polymer network polymeric matrix and at least 0.1percent by weight of self-lubricating particles having a particle sizeless than 500 microns effectively bonded to and distributed in thepolymeric matrix. Preferably the bond strength between the tooth and thedenture base is at least 4,480 psi.

“Wax-like” as used herein refers to material which is flowable (fluid)above 40° C., and becomes dimensionally stable (solidifies: i.e. isnonfluid) at least at and below 23° C., within 5 minutes. Thus, wax-likematerial is flowable when it is at and above 40° C., and becomesdimensionally stable when it is at and below 23° C. Flowable wax-likematerial having a temperature from 100° C. to 40° C., becomesdimensionally stable within 5 minutes by cooling by exposure to anambient temperature between 23° C. and 0° C. Flowable wax-like materialhaving a temperature from 100° C. to 40° C., becomes dimensionallystable within (in order of increasing preference) 2, 1, 0.5 or 0.3minutes by cooling by exposure to an ambient temperature between 23° C.and 0° C.

“High strength dental polymeric material” as used herein refers tomaterial having a polymeric matrix having a flexural modulus of at least250,000 psi and a flexural strength of at least 5,000 psi. Optionally,high strength dental polymeric material includes reenforcing filler.However, the polymeric matrix alone (without any reenforcing filler) hasa flexural modulus of at least 250,000 psi and a flexural strength of atleast 5,000 psi. Preferably high strength dental polymeric material hasa polymeric matrix having a flexural modulus of at least 300,000 psi anda flexural strength of at least 7,000 psi, and an un-notched impactstrength of at least 2 foot-pounds/inch². More preferably high strengthdental polymeric material in order of increasing preference has apolymeric matrix having a flexural modulus of at least 350,000 psi and aflexural strength of at least 12,000 psi, and an un-notched impactstrength of at least 3.0 foot-pounds/inch. High strength dentalpolymeric material is preferably formed into dental products includingfull dentures, partial dentures, denture relines, night guards, crownsand bridges by polymerization of wax-like polymerizable dental material.

“Flexural strength, and flexural modulus” as used herein refers toresults of testing according to ASTM D790 (1997). “Notched impactstrength” as used herein is also referred to as “notched Izod impactresistance” and refers to results of testing according to ASTM D256(1997). “Un-notched impact strength” as used herein refers to results oftesting according to ASTM D4812 (1993).

In the following examples, unless otherwise indicated, all parts andpercentages are by weight; Lucirin TPO refers to2,4,6-trimethylbenzoyldiphenylphosphine oxide made by BASF, and thevisible light curing unit used was a TRIAD VLC visible light curing unitmodified by adding a fifth light to provide about 30 milliwatts/cm² offrom 350 to 450 nm light.

EXAMPLE 1 Preparation of Oligomer

A reactor was charged with 1176 grams oftrimethyl-1,6-diisocyanatohexane (5.59 mol) and 1064 grams of bisphenolA propoxylate (3.09 mol) under dry nitrogen flow and heated to about 65°C. under a positive nitrogen pressure. To this reaction mixture, 10drops of catalyst dibutyltin dilaurate were added. The temperature ofthe reaction mixture was maintained between 65° C. and 140° C. for about70 minutes and followed by additional 10 drops of catalyst dibutyltindilaurate. A viscous paste like isocyanate end-capped intermediateproduct was formed and stirred for 100 minutes. To this intermediateproduct, 662 grams (5.09 mol) of 2-hydroxyethyl methacrylate and 7.0grams of BHT as an inhibitor were added over a period of 70 minuteswhile the reaction temperature was maintained between 68° C. and 90° C.After about five hours stirring under 70° C., the heat was turned off,and oligomer was collected from the reactor as semi-translucent flexiblesolid and stored in a dry atmosphere.

EXAMPLE 2 Preparation of Monomer

A reaction flask was charged with 700 grams of 1,6-diisocyanatohexaneand heated to about 70° C. under a positive nitrogen pressure. To thisreactor were added 1027 grams of 2-hydroxyethyl methacrylate, 0.75 gramof catalyst dibutyltin dilaurate and 4.5 grams of butylated hydroxytoluene (BHT). The addition was slow and under dry nitrogen flow over aperiod of two hours. The temperature of the reaction mixture wasmaintained between 70° C. and 90° C. for another two hours and followedby the addition of 8.5 grams of purified water. One hour later, thereaction product was discharged as clear liquid into plastic containersand cooled to form a white solid and stored in a dry atmosphere.

EXAMPLE 3 Preparation of Polymerizable Denture Contour Material

A wax-like polymerizable dental material was prepared by stirring at 85°C. a liquid mixture of 63.0 grams of oligomer made the procedure ofExample 1 and 37.0 grams of compound of Example 2. 0.35 gram of2,4,6-trimethylbenzoyldiphenylphosphine oxide, (Lucirin TPO made byBASF), 0.5 gram of solution containing 8.3% camphorquinone (CQ), 25%ethyl 4-dimethylaminobenzoate (EDAB) and 66.7% 1,6-hexanedioldimethacrylate (HDDMA).

EXAMPLE 4 Preparation of Polymerizable Denture Base Plate (or Reline)Material

A light curable polymerizable material was prepared by stirring at 85°C. a liquid of 98.0 grams of TBDMA oligomer of Example 1, 0.35 gram of2,4,6-trimethylbenzoyldiphenylphosphine oxide, (Lucirin TPO made byBASF), 1.5 gram of solution containing 8.3% camphorquinone (CQ), 25%ethyl 4-dimethylaminobenzoate (EDAB) and 66.7% 1,6-hexanedioldimethacrylate (HDDMA), 0.1 gram of red acetate fibers and 0.05 gram ofpigment.

EXAMPLE 5 Preparation of Polymerizable Wax-Like Denture Contour Material

A light curable wax-like polymerizable dental material was prepared bystirring at 85° C. a liquid mixture of 50.5 grams of oligomer of Example1, 45.0 grams of monomer of Example 2 and 4.0 grams of stearyl acrylatefrom Sartomer. To this mixture were added 0.35 gram of2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO), 0.1 gram ofred acetate fibers and 0.05 gram of pigment concentrates. Thepolymerizable wax-like material formed becomes flowable at 65 to 68° C.

EXAMPLE 6 Preparation of Polymerizable Denture Set-Up Material

A light curable polymerizable material was prepared by stirring at 85°C. a liquid mixture of 84.5 grams of oligomer of Example 1 and 15.0grams of monomer of Example 2. To this mixture, 0.35 gram of2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO), 0.1 gram ofred acetate fibers and 0.05 gram of pigment were added.

EXAMPLE 7 Preparation of a Denture without Forming a Mold Cavity of aDenture Base

A plaster cast of a patient's mouth is coated with a release agent(e.g., Al-Cote and Isolant sold by Dentsply International Inc. or Teflonsolution such as Krytox from Dupont) and heated to 55° C. in anincubator. An arch-shaped baseplate resin containing 14 grams of theproduct product of Example 4 is applied and shaped onto the warm cast.The resin is shaped and flowed to fully cover the cast, using fingerpressure and trimming to form a baseplate. The baseplate is cured for 10minutes in the visible light curing unit. A sufficient quantity of theproduct of Example 6 is formed into a rope. The rope is applied to thebaseplate. Then artificial teeth are pressed into the rope with thethickness of the rope adapted to adequately cover the appropriatesurfaces of the teeth to provide support. Melted product of Example 5from an about 87° C. wax pot is applied by using an electric spatulabetween the teeth and the baseplate to fully embed teeth and to flowinto fissures between teeth and to smooth the outer surface of thedenture. Hot air from a small nozzle hot air gun may also be applied tolet the product of Example 5 flow into fissures between teeth and smooththe outer surface of the denture. The lingual and buccal surfaces of thedenture are contoured, trimmed and carved using a spatula. The dentureis placed in a patient's mouth for try-in at a dental office and toothpositions are adjusted. The denture back is fitted to the cast and theTRIAD Air Barrier Coating is painted on the denture. Then a modelrelease agent (MRA) sold by Dentsply International Inc. is applied toaround posterior teeth and supporting resin. A strip of Triad gel isapplied on surface between teeth and supporting resin to form acontinuous circle and cured in a visible light curing unit for 10minutes, followed by post curing for 8 hours of gradually cooling to 23°C. When cured, the denture is washed with water to remove all traces ofAir Barrier Coating. The denture is then finished and polished.

EXAMPLE 8 Preparation of a Partial Denture without Forming a Mold Cavity(Investment) of a Denture Base

A removable partial denture framework is fabricated. A separating mediumis applied to a gypsum cast of the patient''s dentition. A sufficientquantity of the product of Example 4 is applied onto the edentulousareas of the cast and adapted with finger pressure or appropriateinstruments. Excess material is trimmed with a hot spatula. A sufficientquantity of the product of Example 4 is adapted into the tissue sidefinish line of the partial denture framework. The framework is seated onthe cast firmly, embedding the uncured material of Example 4. All restsand tissue stops are varnished as correctly positioned on the cast,indicating that the framework is fully seated. Excess material isremoved and these baseplate areas are cured in the visible light curingunit. A rope of the product of Example 6 is adapted onto the precuredbaseplate/edentulous areas. The rope has a thickness sufficient to coverthe ridge lap surfaces of the teeth to provide support for the teeth andto seat the teeth, which are then set up in the rope. A portion theproduct of Example 5 is applied between the teeth and the baseplate. Asmall nozzle hot air gun is used to melt the product of Example 5 sothat it flows into the fissures between teeth as the outer surfacesmoothes. The lingual and buccal surfaces of the edentulous areas arecontoured, trimmed and carved using an electric hot spatula, sharp toolsand hot air gun. The partial denture wax-up is removed from the cast fortry-in. The denture is placed in a patient's mouth for try-in at adental office and tooth positions adjusted if needed. The partialdenture is fitted to a modified cast (reduced soft tissue heights ofcontour). TRAID Air Barrier Coating is painted onto the denture. Then amold release agent (MRA) sold by Dentsply International, Inc. is appliedaround the postierior teeth and supporting resin. A strip of triad gelis applied between teeth and on the surface of the supporting resin toform a continuous circle. The denture is then cured in the visible lightcuring unit for 10 minutes, followed by cooling over a 2 hour period to23° C. When cured, the partial denture is washed with water to removeall traces of Air Barrier Coating. The partial denture is then finishedand polished.

EXAMPLE 9 Preparation of a Night Guard without Forming a Mold Cavity ofa Night Guard

A plaster cast of a patient's teeth is coated with a release agent. 20grams of the product composition of Example 3 is applied over therelease agent and warmed to 50° C. in an oven. The composition is shapedusing finger pressure and trimming to form a night guard which hardenswhen cooling to room temperature. The surfaces of the night guard arecontoured, trimmed and carved using an electric hot spatula and hot airgun. After the night guard is examined and adjusted to fit articulator,the night guard is fitted to the cast and a TRAID Air Barrier Coating ispainted on the denture and cured for 10 minutes. The clear night guardis then washed with water to remove all traces of Air Barrier Coating.The night guard is then finished and polished.

Example 7B of U.S. Pat. No. 6,057,383 (and Canadian Patent Application2207351) was followed and the polymeric product thereof was tested toprovide the information in the following Table. The polymerizablewax-like material of the present invention made by following theprocedure of Example 5 was polymerized and the polymeric product wastested to provide the information in the following Table. Comparing thetest results, Example 5's flexural strength is more than 500 percentgreater than that of the tested material of U.S. Pat. No. 6,057,383.Example 5 of the present invention has a flexural modulus which is morethan two times greater than that of the polymerizable wax-like materialof U.S. Pat. No. 6,057,383. Example 5 of the present invention has anun-notched Impact Strength which is more than eight times greater thanthat of the polymerizable wax-like material of U.S. Pat. No. 6,057,383.Example 5 of the present invention has a notched Impact Strength whichis more than two times greater than that of the polymerizable wax-likematerial of U.S. Pat. No. 6,057,383. Overall results show that thematerial of the invention is suitable for making a denture while theflexural strength and un-notched impact strength of the comparativeexamples are insufficient.

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TABLE COMPARISON OF POLYMERIZABLE WAX-LIKE MATERIALS Flexural FlexuralUn-notched Notched Impact strength Modulus Impact Strength Strength(psi) (kpsi) (ft-lbf/in) (ft-lbf/in²) U.S. Pat. 2897 207.9 0.51 0.53 No.6,057,383 (Ivoclar) Example 7B Example 16820 446.5 4.45 1.28 5 of thepresent invention

It should be understood that while the present invention has beendescribed in considerable detail with respect to certain specificembodiments thereof, it should not be considered limited to suchembodiments but may be used in other ways without departure from thespirit of the invention and the scope of the appended claims.

1. A method of making a dental product, comprising: providing a lightcurable material comprising a polymerizable urethane compound formed bya process comprising reacting a diol compound with a diisocyanatecompound, forming said light curable material, and polymerizing saidlight curable material to form a dental product comprising high strengthdental polymeric material having an un-notched impact strength of atleast 4 foot-pound/inch², a flexural modulus of at least 350,000 psi anda flexural strength of at least 7,000 psi.
 2. The method of claim 1wherein said light curable material comprises a polymerizable urethanecompound having a structure within the scope of the general formula:CH₂═C(R₃)—CO₂—R₄—CO—NH—(R₁—NH—CO—O—R₂—O—OC—NH)_(n)—R₁—NH—CO—R₄—O₂C—C(R₃)═CH₂wherein R₁ and R₂ each independently is an alkyl having from 1 to 14carbon atoms or an aromatic group having from 6 to 14 carbon atoms, R₃is hydrogen, or an alkyl, and R₄ is an alkyl having from 1 to 14 carbonatoms, and n is an integer up to
 20. 3. The method of claim 1 furthercomprising: providing a cast of a patient, forming said light curablematerial on said cast.
 4. The method of claim 1 wherein said polymericmaterial a flexural modulus of at least 400,000 psi and a flexuralstrength of at least 12,000 psi.
 5. The method of claim 1 wherein saiddental product is a denture.
 6. The method of claim 1 wherein saiddental product is a full denture, partial denture, night guard orbridge.
 7. The method of claim 1 wherein said cast has a shape selectedfrom the group consisting of said patient's mouth and said patient'steeth.
 8. The method of claim 1 wherein said polymerizable urethanecompound is form from an isocyanate end-capped intermediate.
 9. Themethod of claim 1 wherein said polymerizable urethane compound is formedfrom a viscous paste-like diisocyanate end-capped intermediate.
 10. Themethod of claim 1 wherein said diisocyanate compound has a structurewithin the scope of the general formula:OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—R₁—NCO wherein R₁ and R₂ are alkylhaving from 1 to 14 carbon atoms or an aromatic group having from 6 to14 carbon atoms, m is an integer up to
 20. 11. The method of claim 1wherein said diol compound and said diisocyanate compound form anintermediate compound having a structure within the scope of a generalformula selected from the group consisting of:OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m—(R) ₁—NH—CO—O—R′₂—O—OC—NH)_(n)—R₁—NCO,OCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—(R″₁—NH—CO—O—R₂—O—OC—NH)_(n)—R′₁—NCO andOCN—(R₁—NH—CO—O—R₂—O—OC—NH)_(m)—(R″₁—NH—CO—O—R′₂—O—OC—NH)_(n)—R′₁—NCOwherein R₁ and R₂ each independently is an alkyl having from 1 to 14carbon atoms or an aromatic group having from 6 to 14 carbon atoms, andn is an integer up to
 20. 12. The method of claim 1 wherein saidurethane compound is formed from a isocyanate end-capped intermediateand a hydroxylalkymethacrylate.
 13. The method of claim 1 wherein saiddiisocyanate is trimethyl-1,6-diisocyanatohexane, and said diol isbisphenol A propoxylate.
 14. The method of claim 1 wherein said highstrength dental polymeric material has an un-notched impact strength ofat least 4.4 foot-pound/inch².
 15. The method of claim 1 wherein saidurethane compound is formed from trimethyl-1,6-diisocyanatohexane,bisphenol A propoxylate and 2-hydroxyethyl methacrylate.
 16. The methodof claim 1 wherein said polymerizable urethane compound has an aromaticgroup.